Abstract: Thin film lubrication (TFL) has been a research hot spotin recent years, which leaves many black areas to tribologists. Themicropolar theory for fluids is adopted to account for the microstructureand microrotation in TFL. Simulation results reveal that micro-polarity willgive rise to an increase in effective viscosity. Micro-polarity has littleeffect on the pressure profile and film shape, but has an influence on thefilm thickness in TFL. The effective viscosity grown with micro-polarity isin very close to that of experimental results presented in a preceding work.The present work will shed some light into the mechanism of TFL.